The ability to detect chemical and biological species rapidly with specificity and at very low concentrations is becoming increasingly important, particularly in the medical, environmental and forensic areas Detection of low levels pathogenic species such as agents that pose a biological threat, for example, provides a crucial measure of environmental contamination by such agents since their existence, even at low concentrations, can have serious pathological consequences. Sensitive detection devices therefore, enables the elimination of such pathogens prior to their causing significant harm. There is also a growing need for the rapid and quantitative detection of biological species in a number of biomedical applications, and the healthcare and food industries.
Chemical sensors disclosed in the art commonly utilize solid semi-conductor materials such as metallic oxides as sensor probes. Detection of target species by these sensors is typically accomplished by measuring a change in electrical resistance or optical property of the probes caused by adsorption of the species on the probe material surface. To provide adequate sensitivity however, such sensors have to operate at elevated temperatures to cause an increase in chemical reactivity of the target species to the probe surface. Other limitations of prior art probes include long recovery times, poor specificity and reproducibility, and their inability to be specifically adapted for detection of a wide range of chemical and biological species.
Biological sensing devices offer the potential for providing high a degree of specificity and good sensitivity, but remain largely unexplored due to technical and chemical issues pertaining to their structure-property characterization. Although charge transport properties of certain macromolecules such as DNA have been studied, their application as sensors has not been explored. This may be attributed to the inadequate understanding of the nature of the intrinsic properties of DNA, which has proven difficult to study directly using presently available systems.
Nanotechnological approaches to molecular electronics (“molectronics”) although theoretically feasible for sensor applications on the other hand, has not been practically realized mainly because they require materials with programmable structural and electronic characteristics.
In view of the above, there is a need for sensing devices that provide a highly sensitive and specific response to target species requiring detection, but more desirably, provide a tunable response to a variety of chemical and biological species that pose pathological hazards to the environment.